For conveying workpieces, for example in transfer lines, respectively production lines, conveying devices are provided. Here the workpieces are conveyed in the direction of the production sequence on a driving line designed, for example, as a roller conveyor. The driving line is divided into sections so that the advance of the workpieces can be influenced section by section. If, for example, the driving line is designed as roller conveyor, the rollers, respectively simultaneously several rollers in a section, are driven by corresponding drives. For that purpose a plurality of back-geared motors is provided. These can be switched on and off. It is often an object that a workpiece positioned in a section can be controlled consciously, resulting in a very large number of back-geared motors when, for example, small workpieces are conveyed. This may lead to space problems, as the drives have to be arranged because of their plurality, if necessary, on both sides next to the roller conveyor. By means of that also the access at the belt itself is impeded. These handicaps in the accessibility disturb in particular the feeding or removal of workpieces. Also the construction space for the necessary guides for the workpiece and holding devices with sensory mechanism, which may be provided, is considerably limited. The overall technical effort becomes very large altogether because of the high number of back-geared motors, their cabling and control.
In the solution according to the citation DE 40 02 414 A1 the conveying device is divided into different sections. The production line here has a conveyor road where workpieces, for example workpieces clamped on workpiece carriers, are conveyed with identical speed from one production station and one production area to the other.
The solution according to the citation DE 40 02 414 A1 suggests assigning an additional conveyor to the production station, respectively several production stations of the production line. This additional conveyor has another construction than the conveyor road itself. It connects the production stations of the production area following one another at a distance and extends in addition to that over a feeding road arranged in front of the first production station seen in the conveying direction and a removing road attached to the last production station. The additional conveyor has essentially only a longish means of drawing which can move back and forth in the direction of the conveying. The conveying road, which is furthermore continues over the region of the additional conveyor, namely the friction roller conveyor, which is not driven in this region, serves as a means for carrying for the additional conveyor. In this region of the conveying road the drawing means of the additional conveyor takes over the drive for these parts. A stationary driving unit driving the connecting rod via a pinion is provided for this additional drive which may, for example, drive workpieces, respectively workpiece carriers, in several sections. The connecting rod engages via couplings which are formed like claws into the workpiece carriers and therefore drives them for the movement on the conveying road.
Coming from the state of the art described above it is an object of the invention to provide a conveying device where the effort for the corresponding conveying system is clearly reduced.